Method and compositions for cleaning ovens and the like

ABSTRACT

A METHOD IS PROVIDED WHEREBY BAKED ON ORGANIC DEPOSITS FROM A SURFACE ARE READILY REMOVABLE WHEREIN AN ALKALI METAL BICARBONATE IS APPLIED TO THE CLEAN SURFACE AND SUBSEQUENT CLEANING AFTER SOILING IS EFFECTED BY WASHING OF THE SURFACE TO REMOVE THE SOILED COATING. COMPOSITIONS ARE PROVIDED FOR USE IN THE PROCESS WHICH INCLUDE IN ADDITION TO THE ALKALI METAL BICARBONATE, AN AQUEOUS VEHICLE AND A SURFACE ACTIVE AGENT. OTHER ADDITIVES MAY ALSO BE INCLUDED IN THE COMPOSITIONS SUCH AS SUSPENSING AGENTS, CORROSION INHIBITORS, GELLING AGENTS AND COLORING MATERIALS. THE PROCESS MAY BE CARRIED OUT BY APPLYING THE COMPOSITIONS BY MEANS OF A SPONGE, BRUSH OR CLOTH, FROM A SPRAY BOTTLE OR BY MEANS OF AN AEROSOL TYPE PRESSURIZED DISPENSER.

United States Patent 3,672,993 METHOD AND COMPOSITIONS FOR CLEANINGOVENS AND THE LIIGE Harry Ian Mitchell, Rochdale, and Kenneth Tomlinson,Bramhall, England, assignors to Colgate-Palmolive Company, New York,N.Y. No Drawing. Filed July 30, 1970, Ser. No. 59,753

Int. Cl. C23g 1/02 US. Cl. 134-3 9 Claims ABSTRACT OF THE DISCLOSURE Amethod is provided whereby baked on organic deposits from a surface arereadily removable wherein an alkali metal bicarbonate is applied to the.clean surface and subsequent cleaning after soiling is effected bywash- I This invention relates to the cleaning of surfaces, such as thesurfaces of ovens, which are subjected to heat and are liable to soilingby baked-on organic deposits.

The soiling matter deposited on ovens, such as domestic cooker ovens,consists of a complex organic mixture of natural fats and other depositsfrom the cooking of food. When heated at normal oven temperatures, thissoiling matter is converted into an infusible polymeric mass in whichpart of the organic material may also be charred. Detergents, scouringpowders and similar cleansing products, even when alkaline (e.g. thosecontaining phosphates), although highly efiicient for removing normalgreasy soiling matter, are not usually adequate for removing baked-onsoil of the type found in ovens.

The removal of this type of soil is therefore a considerable problem,requiring powerful chemical or physical action. Among the most effectivechemical compounds known for this purpose are the caustic alkalis,sodium and potassium hydroxides. Their mode of action is that they reactwith and hydrolyse natural fats, thus converting them at least partiallyinto their sodium or potassium salts, which are water-soluble and thuseasily removed. Commercial products of this type usually contain up to3% of sodium hydroxide together with other components such as solventsand emulsifiers which promote the efiiciency of the product. They may beapplied direct by brush or sponge, or more conveniently by means of anaerosol spray. Products of this type, although efficient in theiraction, suffer from a number of major disadvantages. The most importantdisadvantage is'the serious hazard to the eyes and skin arising from theuse of caustic alkalis. If inadvertently sprayed in the eyes, a productof this type could cause permanent blindness. It is also common practicefor housewives to use rubber gloves when applying a product of this typeto avoid damage to the skin. Such products may also damage adjacentsurfaces, such as paint, aluminum or wood, onto which they may beinadvertently sprayed. Another disadvantage is that such products whenapplied to soiled oven surfaces must attack the soiling matter from theouter surface, while the most severe charring and polym erisation isgenerally present in the interior of the soil 3,672,993 Patented June27, 1972 layer, adjacent to the oven wall. This makes cleaning morediflicult.

Alkalis less alkaline than caustic sodi, although they would avoid someof the hazards already indicated, are not very effective in hydrolyzingbaked-on fat in the short time of application, and consequently are notefficient oven cleaners.

Certain pre-treatment preparations are known which act by forming aphysical barrier between the oven wall and the soiling matter, and donot depend on chemical actions. Those preparations are expensive and notvery effective.

It is an object of this invention to avoid the disadvantages of theknown oven cleaner preparations, and at the same time to provide asimple and effective procedure for oven cleaning.

According to one aspect of the invention a method of cleaning a surfacewhich is subjected to heat and is liable to soiling 'by baked-on organicdeposits comprises applying to the clean surface an alkali metalbicarbonate, and washing the surface clean again after such soiling.

According to other aspects of the invention there are provided variouscompositions for the pre-treatment of such a surface and comprising analkali metal bicarbonate, an aqueous vehicle and other components ashereinafter described.

According to a further aspect of the invention there is provided apressurized aerosol-type dispenser containing a solution or suspensionof an alkali metal bicarbonate and a propellant.

The principle of the invention is as follows: Alkali metal bicarbonates,which are very mild alkalis, decompose on moderate heating to form thecorresponding carbonates which are much stronger alkalis. Thesecarbonates in turn are sutficiently powerful to promote the slowhydrolysis of fats, particularly under the influence of temperature.After application of the alkali metal bicarbonate to the clean ovensurface, use of the oven converts it to the corresponding carbonate,which slowly hydrolyses fats deposited on the walls, thereby convertingthem at least partially into the corresponding soaps which are easilyremoved with warm Water.

Alkali metal bicarbonates are very mild alkalis which cannot harm theeyes or the skin. They are harmless to painted surfaces, aluminium andwood, all of which may be damaged by caustic alkalis. Since the productis applied -directly on the clean oven walls, it acts first on the fatwhich is first deposited and is therefore most likely to polymerize andchar and be the most intractable.

Oven pre-treatments according to the invention can be effected in avariety of ways, the following being typical examples:

(a) Application of a solution or suspension of alkali metal bicarbonateby means of a sponge, brush or cloth.

(b) Applicable of a solution or suspension of alkali metal bicarbonateby means of a hand operated spray bottle or a hand pump or automatically(e.g., by venture action) by means of a cartridge of compressed gas.

(c) Application of a gel or paste composition containing alkali metalbicarbonate.

(d) Application of a solution or suspension of alkali metal bicarbonateby means of an aerosol type pressurized dispenser.

The ways (b) and (d) are preferred.

Examples of suitable alkali metal bicarbonate are sodium bicarbonate,potassium bicarbonate and mixtures thereof.

The basic material is a solution or suspension of the alkali metalbicarbonate in water. For a solution the amount present is governed bythe solubility of'the partic ularsaltjn water. Typical approximatefigures are:

Sodium bicarbonate-8% at 20 C. Potassium bicarbonate25% at 20 C.

These and all other percentages are by weight.

On the grounds of cost, sodium bicarbonate is preferred, and a solutionof .4% to 7% is sufiicient to give adequate performance. It is possibleto produce a stronger material by including additional alkali metalbicarbonate in a suspended form.

Other,materials may be added for imparting desired additionalproperties. Examples are:

(i) SURFACE-ACTIVE AGENTS Such compounds improve the wetting action,afford moreeveu distribution on the oven walls. They may also act as amild adhesive improving retention of the filmon the oven wall. Theymayalso act as emulsifying agents for water-immiscible propellants used inaerosol dispensers. In so far as they withstand oven heat they may alsofacilitate washing off of the soil layer. Almost any kind ofsurface-active agent will perform at least one of these functions tosome extent.. However, among the most eflicient are:

Ethoxylated nonyl phenols (especially 8-11 mols ethylene oxide),

Phosphate ester (e.g. Solumin PFN 95 manufactured by Glovers ChemicalsLtd. of England),

Sodium dodecylbenzene sulphonate.

(iii) CORROSION INHIBITORS These may be included to inhibit corrosion ofthe aerosol can and oven walls. Examples are sodium benzoatefso diumnitrite and mixtures thereof.

(iv) COLORING MATERIALS A coloring material such as a dye or pigmentmaybe added to afford a visual contrast between the oven wall and theapplied composition to facilitate uniform and complete application, ormerely to alter the appearance of the resulting dried film which in theabsence of added color has a whitish hue. 7

(v) GELLING OR THICKENING AGENTS Materials such as carboxymethylcellulose may be added to gel or thicken compositions of the type (c)above.

(vi) PROPELLANTS For aerosol type products a wide variety} of propellantsubstances may be used, such as halocarbons, hydrocarbons, carbondioxide, nitrous oxide or suitable mixtures thereof, though hydrocarbonsare not recommended because of flammability hazards. "t'l Thepressurized dispenser is preferably of a type which discharges theproduct asa spray.

The following examples illustrate the inventiomln each case a baseformula is given which may be applied direct weights are used:

' Example I Base formula: Percent Sodium bicarbonate 7 Nonyl phenolpolyethoxylate (8-9 ethylene oxides) e.g. Ethylan TU (Lankro chemicalsLtd., England) 1.5

Sodium xylene sulphonate (30%- aqueous soltion) 1.5

- Water 90.

For filling into an aerosol dispenser the following weights are used:

. Percent Base as above 90 Difiuorodichloromethane 5Tetrafluorodichloroethane 5 "Example II Base formula: Percent Potassiumbicarbonate 15.00 Sodium salt of disulphonated dodecyldiphenyloxide (45%aqueous solution) (Dowfax 2A1) Nonylphenol polyethoxylate (8-9 ethylene1 oxides) e.g. Ethylan TU (Lankro Chemicals Ltd.) 0.15 Water 84.45

For filling into an aerosol dispenser the following 7 Percent Base asabove 90 Difiuorodichloromethane 5 Tetrafluorodichloroethane S I AExample III Base formula (with suspended solids): Percent Sodiumbicarbonate 16.0 Hydratedsilica (Aerosil 200 Degussa) 1.0

Sodium salt of disulphonated dedecyldiphenyloxide 45% (Dowfax 2A1) 1.0

Water 82.0

For filling into an aerosol dispenser the following weights are used:

, I Percent Base as above a 80.0 Difluorodichloromethane 10.0Tetrafluorodichloroethane 10.0

Products manufactured according to the examples were evaluated by theprocedure described below.

Enamelled metal plates 18" x 10" were heated to 100 C. in an oven. Thehot plates were removed from theoven and a mask was placed over one halfof each plate. The uncovered half of each plate was then treated withthe product under test. After drying the plates the whole area wascoated evenly with a layer of greasy soiling matter (deep frying cookingfat, lard and tallow to the oven walls by any convenient means. Inaddition details are given for the application of the same base by meansofanaerosol dispenser. V

were'used as typical soiling materials.) The plates were then heated inan oven for at least24hours at temperatures between 200 and 250, C.After removal from the oventhe plates were cooled. The whole surface ofthe plates was then washed with a /z% solution of soap in warm'waterapplied by a sponge. The burnt-on soiling matter was completely removedfrom thevtreated areas without difliculty. The untreated areas werestill heavily soiled with burnt-on fat after the treatment.

What is claimed is:

1. A method of cleaning a surface which is subjected to heat and isliable to soiling by baked-on organic deposits which comprises applyingto the clean surface an effective amount of an alkali metal bicarbonate,and washing the surface clean again after such soiling.

2. A method as claimed in claim 1 in which the alkali metal bicarbonateis applied as a solution in an aqueous vehicle.

3. A method as claimed in claim 1 in which the alkali metal bicarbonateis applied as a suspension in an aqueous vehicle.

4. A method as claimed in claim 3 in which the suspension also containsa suspending agent.

5. A method as claimed in claim 1 in which the alkali metal bicarbonateis applied in the form of a gel or paste.

6. A method as claimed in claim 5 in which the gel or paste alsocontains a gelling or thickening agent.

7. A method as claimed in claim 1 in which the alkali metal bicarbonateis applied in the form of a solution or suspension sprayed from apressurized container.

8. A method as claimed in claim 1 in which the alkali metal bicarbonateis applied together with a surfaceactive agent.

9. A method as claimed in claim 1 in which the alkali metal bicarbonateis selected from sodium bicarbonate, potassium bicarbonate and mixturesthereof.

References Cited UNITED STATES PATENTS 3,183,110 5/1965 Aler et al 2523,198,744 8/1965 Cook et a1. 252156 FOREIGN PATENTS 751,361 1/1967Canada 252156 US. Cl. X.R.

